88 



The Endocrine Organs 



of the excised eye of the frog (W. Cramer). In some of these actions it re- 

 sembles adrenalin, but the stimulating autacoid of the pituitary is certainly 

 different both chemically and in its physiological reactions from that of 

 the suprarenal. For it does not specifically stimulate structures innervated 

 by the sympathetic as does adrenalin ; moreover, neither apocodeine nor 

 ergotoxine affect the results obtained with it. Probably it acts as a direct 

 stimulus upon the contractile substance of the cells which it influences. 



Effects on Kidney. The renal arteries form an exception to the con- 

 strictor effect produced by pituitary extract, since they dilate as a con- 

 sequence of the addition of the extract to the circulating blood (fig. 60) : 

 the dilatation is correlated with an increase of secretion of urine (figs. 60, 



FIG. 59. Tracing showing the action on an isolated cornu of rat's uterus suspended in Locke's 

 solution, of the addition of extract of posterior lobe of ox pituitary to the solution. (M. Itagaki.) 



61, 62): it is often preceded by a slight contraction, and the increase of 

 urine by a temporary diminution. The increased secretion may be in part 

 brought about by the increased flow of blood through the kidney vessels, 

 due to the circumstance that they undergo dilatation, while all the other 

 systemic arteries are contracting ; but that it is to a certain extent caused 

 by a specific effect of one of the pituitary autacoids is probable from the 

 fact that it may occur in the absence of any obvious arterial change. 



Moreover, an increased rate of flow is maintained after the blood-pressure 

 has come back to the level at which it stood before the injection. And the 

 effect of a second and subsequent doses of the autacoid administered soon 

 after the main result of the first dose has passed off is again to produce an 

 increase in the urine flow (fig. 62), although the blood-pressure as the result 

 of these after-doses does not rise, or falls instead of rising, and although 

 the kidney volume may now be unaffected. This experiment clearly 



